Fluid-operated devices

ABSTRACT

A monostable pure fluid device is described in which the values of the control pressures at which the power stream is switched from its normal outlet and at which the power stream resets to its normal outlet respectively are substantially equal. The reaction chamber of the device has substantially parallel top and bottom surfaces and a small interruption is formed in one of the surfaces by a projection, step or depression in the surface.

United States Patent Brian John Steptoe [72] inventors Hitchln; Sidney Ties, Stevenage; William Cecil Morton, Biggleswade, all of, England [21] Appl. No. 719,904 [22] Filed Apr. 9, 1968 [45] Patented July 13, 1971 l 73] Assignee International Computers and Tabulators Limited London, England [32] Priority Apr. 22, 1967 [33] Great Britain [3 1 1 186 13/67 [54] FLUID-OPERATED DEVICES 3 Claims, 6 Drawing Figs.

[52] US. Cl 137/815 (51] Int. Cl. FlSc l/10 [50] Field of Search 137/815 [56] References Cited UNITED STATES PATENTS 3,444,879 5/1969 McLeod,Jr. 137/815 3,181,545 5/1965 Murphy,Jr. 137/815 3,240,219 3/1966 Dexter et a1. 137/815 3,244,189 4/1966 Bailey 137/815 3,272,214 9/1966 Warren 137/815 3,279,488 10/1966 Jones 137/815 3,294,103 12/1966 Bowles 137/815 3,366,131 1/1968 Swartz 137/815 Primary Examiner- Samuel Scott Attorney-Plane and Baxley ABSTRACT: A monostable pure fluid device is described in which the values of the control pressures at which the power stream is switched from its normal outlet and at which the power stream resets to its normal outlet respectively are substantially equal. The reaction chamber of the device has substantially parallel top and bottom surfaces and a small interruption is formed in one of the surfaces by a projection, step or depression in the surface.

PATENTEI] JUL] 319?: 3,592,210

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FLUID-OPERATED DEVICES BACKGROUND OF THE INVENTION.

The present invention relates to fluid-operated devices and in particular to pure fluid monostable switching devices.

Pure fluid amplifiers have previously been proposed and in these devices a stream of fluid, usually termed the power stream, issuing into a reaction chamber is diverted to one or another of at least two outlets from the chamber by, for example, the interaction with the power stream of a control stream of fluid applied from a further inlet at an angle to the power stream. In one form of device the power stream is, in the absence of a control stream, arranged to ,issue from a particular one of the outlets and is switched or diverted to asecond outlet only when the control stream is present. This form of device is therefore monostable, and such monostable devices have commonly been proposed to form logic gates in pure fluid logic networks built-up by interconnecting the inlets and outlets of a number of pure fluid devicesPrior monostable devices suffer from a hysteresis effect so that the control pressure required to switch the power stream from its stable state is considerably greater than the control pressure at which the power stream reverts to its stable state.

U.S. Pat. No. 3,279,488 discloses a pure fluid analog amplifier in which in the interaction region which has no sidewalls and the bottom wall has a cross vent which has a transverse dimension greater than the range of deflection of the power stream of fluid in order to equalize the static pressures on the two sides of the stream. Such a vent also eliminates boundary layer effects and thereby prevents lock-on in a stable path through the interaction region.

SUMMARY OF THE INVENTION.

According to the invention a pure fluid monostable device includes a reaction chamber bounded by sidewalls and by top and bottom walls having substantially parallel planar surfaces; a first outlet and at least a second outlet at one end of the reaction chamber; means to produce a power stream of fluid issuing from the opposite end of the reaction chamber and normally passing to said first outlet; means to produce a control stream of fluid issuing from one of said sidewalls and effective to divert the power stream from said first outlet to said second outlet; and means to provide an interruption to at least one of said planar surfaces over a small area.

The provision of a small interruption in at least one of the planar surfaces is effective to reduce the hysteresis effect in monostable devices so that the control pressures at which the power stream switches and resets respectively are approximately equal.

BRIEF DESCRIPTION OF THE DRAWING.

FIGURE 1 is a diagrammatic representation of a monostable device,

FIGURE 2 shows the relationship between control and output fluid pressures ofa conventional monostable fluid switch,

FIGURE 3 is a diagrammatic representation of another form of monostable device.

FIGURE 4 is a cross section on line 4-4 ofFIG. 1.

FIG. 5 a similar cross section showing a modification.

FIG. 6 is a cross section on line 6-6 of FIG: 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS.

Referring now to FIGS. 1 and 4 of the drawing, a monostable pure fluid switching device is formed by a recess in one surface of a block 1. The device includes a power stream inlet chamber 2 terminating in a power stream orifice 3. A fluid passage 4 is provided in the block 1 opening into the chamber 2 to enable the device to be connected to a source of fluid, such as air, under pressure.

The power stream orifice 3 opens into one end ofa reaction chamber 5 also formed as part of the recess. The chamber 5,

at the opposite end, opens into a pair of diverging outlet passages 6 and 7 respectively, separated by a splitter 8. Each of the passages 6 and 7 is provided with an opening 9 to enable fluid from the reaction chamber 5 to pass out of the device.

The reaction chamber is bounded by sidewalls l0 and 11 respectively. The sidewall 10 is shaped between the power stream orifice 3 and the outlet passage 6 so that a fluid stream issuing from the orifice 3 is constrained by boundary layer effects to follow the sidewall 10 and enter the outlet passage 6 to flow out of the device through the opening 9 in the passage 6. The sidewall 11 is so shaped that no similar boundary layer effect is developed between a fluid stream from the orifice 3 and the sidewall 1 l.

A further orifice 12 is formed in the sidewall 10 and is connected to a control stream chamber 13, which is provided with a passage 14 to enable the chamber 13 to be connected to a control fluid source.

As will be seen in FIGURE 1, the chambers 2 and 13 together with the orifices 3 and 12,-the reaction chamber 5 and the outlet passages 6 and 7 are formed by the shape of a substantially constant depth recess in one face of the block 1. The recess is closed to form the aforementioned chambers, orifices and passages by a closure plate 15, indicated by a dashed outline, secured to the face of the block 1. Thus, the plate 15 and the bottom of the recess in the block 1 together form opposed substantially parallel planar boundaries for fluid channels fonned by the shape of the recess in the block 1. An interruption in the planar surface of the bottom of the reaction chamber is provided by a shallow depression 16 in the bottom of the recess within the reaction chamber 5.

In operation, fluid under pressure is supplied to the power stream chamber 2 through the passage 4. A stream of fluid issues from the power stream orifices 3 into the reaction chamber 5, and this stream is constrained by boundary layer effects to follow the sidewall 10 and enter outlet passage 6 and then leave the device through the associated opening 9. This is the normal stable operating state of the device. If it is required to switch the power stream from the outlet passage 6 to the passage 7, fluid is applied through the passage 14 to the control stream chamber 13 and a fluid control stream then issues from the orifice 12 into the reaction chamber 5. The interaction of the control stream from the orifice 12 with the power stream from the orifice 3 causes the combined stream to be diverted to the opposite side of the splitter 8 to enter the second outlet passage 7 and this stream then leaves the device through the opening 9 associated with the passage 7. The diversion of the fluid stream to the passage 7 is maintained only for so long as the control stream continues to flow. This is the normal mode of operation of a conventional monostable switch.

In the case of conventional switches, which have no depression 16 in the reaction chamber, the switching response of the power stream to the application of a control stream exhibits a hysteresis characteristic. This characteristic is shown in FIG. 2, in which thefluid pressure P0 in the outlet passage 7 is plotted against the control stream pressure Pc. It will be seen that in order to produce switching of the fluid stream from passage 6 to passage 7, the control stream is required to be at a particular pressure Pc 1. When the control stream is at pressure Pc 1, the fluid stream switches rapidly and the fluid pressure P0 in passage 7 rises in consequence. If the control stream pressure is reduced, after the fluid stream has been switched, the restoration of the fluid stream from the outlet passage 7 to the outlet passage 6 does n not take place until a control stream pressure Pc 2 considerably less than the pressure Pc 1 is reached.

The spread of control stream pressures resulting from this hysteresis characteristic greatly reduces the permissible tolerance on the operating pressures of a device. On the other hand, where a number of devices are interconnected in a logic network, for example, it is desirable that the greatest possible tolerance shall be available in the operating characteristics of the i individual devices.

It has now been found that the provision of an interruption, such as the depression 16, in the top or bottom planar surfaces bounding the reaction chamber 5 reduces the spread of the hysteresis characteristic so that the switching pressures Pc 1 and Po 2 are very nearly equal. Thus, the provision of such an interruption ensures that the greatest tolerance on operating pressures is available.

The interruption, as shown in FIGS. 1 and .4, is in the form of a depression 16. However, the interruption may alternatively take the form of a projection or pip. FIGS. 3 and 6 applied to a monostable device having two control streams show such an alternative form. In these figures, similar parts, are referenced with the same numerals as those used in connection with FIG. 1. As before a block 1 has a recess on one surface forming a power stream chamber 2, a power stream orifice 3, a reaction chamber 5 having sidewalls l and. l l, and a pair of outlet passages 6 and 7. In this case two control stream orifices l2 and 17 are provided in the sidewall 10. The orifice l2 communicates with a first control stream chamber 13 having a passage 14 to which a first control stream may be applied, while the orifice l7 communicates with a second control stream chamber 18. The chamber 18 has a passage 19 for connection to a second control stream source. A projection 20 in the bottom of the recess in the block 1 within the reaction chamber provides the required interruption in the bottom planar surface of the device.

As in the case described with reference to FIG. 1, a cover plate 15 is provided over the block 1 in FIG. 3. It will be realized that the interruption in one of the parallel planar surfaces bounding the reaction chamber may be provided in the underside of the cover plate 15 instead of in the bottom of the recess in the block 1.

It is to be understood that although the interruption in the surface in the form of a projection is described in relation to a monostable device having two control streams, it may also be used in the device shown in FIG. 1. Also in the device of PK].

3 a depression may be provided instead of the projection.

The interruption is small in relation to. the size of the reaction chamber, and its width is less than the transverse limits of the fluid stream through the reaction chamber. For example, in an actual case, the recess in the block 1 was 0.35 inch deep,

the power stream inlet orifice was 0.010 inch wide, the reaction chamber at the end remote from the power stream orifice was 0.060 inch wide and the interruption was a depression 0.025 inch diameter and approximately 0.010 inch deep. In another similarly proportioned element the interruption was formed by a pip approximately 0.010 inch in height.

The interruptions need not be circular in plan as shown in FIGS. 1 and 3. A microgroove, some 0.025 inch wide and about 0.10-0.020 inch deep has been found to be effective, as has a form of step 21 (FIG. 5) of about the same depth, the step having the effect of increasing the depth of the recess in the downstream direction. In this case, also, the portions of the reaction chamber both upstream and downstream from the interruption are bounded by substantially parallel an planar top and bottom surfaces.

We claim:

1. A pure fluid monostable device including a reaction chamber bounded by first and second sidewalls; and top and bottom walls having substantially parallel planarsurfaces; first and second outlets at one end of the reaction chamber; means to produce a power stream of fluid issuing from the opposite end of the reaction chamber, the power stream normally being in a first stable state in which it is locked on to said first sidewall and passing to said first outlet; means to produce a control stream of fluid issuing from said first sidewall and effective to divert said power stream from its first stable state to a second unstable state in which it passes to said second outlet;

and an interruption in at least one of said planar surfaces over a small area, the transverse width of the interruption being less than the transverse width of the power stream, said. interruption being located intermediate and spaced from said first and second sidewalls in said reaction chamber and being effective to aid in resetting said power stream from said second outlet to 

1. A pure fluid monostable device including a reaction chamber bounded by first and second sidewalls; and top and bottom walls having substantially parallel planar surfaces; first and second outlets at one end of the reaction chamber; means to produce a power stream of fluid issuing from the opposite end of the reaction chamber, the power stream normally being in a first stable state in which it is locked on to said first sidewall and passing to said first outlet; means to produce a control stream of fluid issuing from said first sidewall and effective to divert said power stream from its first stable state to a second unstable state in which it passes to said second outlet; and an interruption in at least one of said planar surfaces over a small area, the transverse width of the interruption being less than the transverse width of the power stream, said interruption being located intermediate and spaced from said first and second sidewalls in said reaction chamber and being effective to aid in resetting said power stream from said second outlet to said first outlet by switching the power stream back to said first stable state upon only a fractional decrease in pressure of said control stream.
 2. A device as claimed in claim 1 in which said interruption is a depression.
 3. A device as claimed in claim 2 in which the depression has decreasing depth in a downstream direction. 